Forza Horizon Workshop - Building & Tuning

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WrecklessAbandon
Simple enough, as I get cars prepared and customized, I'm going to dish out dirty secrets along the way.

I've been practicing driving, building, tuning, and off-roading in FH2, FH3, and FH4 for about a year and a half now. I wouldn't say I know everything about it, but my goal is to find and uncover the mysteries behind the most complex building and tuning system, in, ever?
I don't know, but what I do know is these games are almost picturesque of a tuner or builders wet dream.
 
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ENGINE:
A simple starter in engine building, is knowing what parts affect the engine (and entire car) in different ways.
Some engine mods remove weight, while others add weight.

Keeping in mind how it affects the cars overall weight balance can be critical, like throwing giant turbos and intercoolers on the front of an already front-heavy vehicle might not be the best method of gaining power.

Parts list -

Air intake - Small weight loss
Has no notable effect on powerband

Intake manifold - Medium weight loss
Has no notable effect on powerband

Fuel upgrades - Usually no change, bigger carbs add weight.
Has no notable effect on powerband

Ignition - No weight change
Has no notable effect on powerband

Exhaust - Large potential weight loss
Has a slight effect on powerband, usually shifting it upwards in the rev range.

Camshafts - No weight change
Can change powerband dramatically, camshafts can be a key to maximizing horsepower at a given PI, by adding power without adding torque.
Camshafts are usually the easiest way to maximize HP, but some times more power can be achieved with less than racing cams, so don't do it blindly

Valves - Small weight loss
Has no notable effect on powerband

Displacement - No weight change
As far as I've seen, usually has no notable effect on powerband

Pistons/Compression - Small weight loss
Has no notable effect on powerband

Turbo/Supercharger - Large potential weight gain
Turbos are the best method of forced induction, usually. Some engines with lots of torque can take advantage of the PI system by utilizing superchargers to bring the torque/horsepower ratio lower.

Intercooler - Large potential weight gain
Has no notable effect on powerband, the extra power often isn't worth the extra weight from what I've seen.
*can be useful to lower PI occasionally

Oil cooler - Medium potential weight gain
Has no notable effect on powerband, and much like the intercooler, has a tendancy not to be worth the added weight.
*can be a good tool to lose a PI or two occasionally

Flywheel - Small/Medium gain*

*It should be noted that flywheel weight loss "should" have a much larger effect than regular weight, around 8x the effect of chassis weight reduction.
I will be testing this out, as some cars can lose 10lbs or more off the flywheel, it should be verifiable in performance.
 
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BRAKES: The first thing to know about braking in Horizon, is that braking distances are really short, which means brakes aren't as important as they could be.

The main reasons to change your brakes are reducing weight, and adding adjustability.

If you're driving something that just won't stop, it's either your brakes or your tires fault.

There are up to 3 available upgrades.

Street: Fancy new parts that are almost stock.
These rarely change vehicle weight, if ever, they simply offer better braking performance, if only slightly.
A good upgrade in-game, not so strong you over-brake, but better than stock.


Sport: Sometimes reducing weight, other times adding weight. (Particularly old cars with terrible brake systems)
Offers a little more braking than level 1.
Most time I think it's better to go with racing brakes or street, because of the PI system.
The street kit should have most cars stopping fast enough that you're really looking for adjustability beyond this kit.
The racing kit usually doesn't cost much more PI, and significantly reduces weight and adds adjustability.


Race: Almost always coupled with weight loss (20-60lbs typically)
These brakes usually reduce a decent amount of weight, while providing maximum stopping power, they also give you the ability to fine-tune your system.
Keep the weight loss in mind when you see a big chunk of PI taken by them.
The only downside is most of the time your brakes are good enough already, skipping brakes is definitely an option sometimes to use PI elsewhere.


SUSPENSION:
A tricky upgrade, it's easy to dive on the racing suspension and call it a day. But is it worth it, and what sacrifices (if any) must you make to use it?

Street: A basic improvement over anything that doesn't have it, this works pretty well off-road too, so if you're crossing country, or just make mistakes and wind up in the dirt, it's a pretty capable kit for all-purpose.

Sport: Similar to street, an obvious in-between street and race. Better on pavement, still not bad off-road.
(This should have a few adjustable settings including springs, dampers, and camber, but it doesn't)

Race: Fully adjustable, and the only adjustable of the road suspensions. If a car or truck doesn't drive well, you almost have no choice, plus there's a pretty good chunk of performance in a racing suspension, right?

Rally: Fully adjustable, but starts you off with the full "Baha treatment". Ride height jacked, everything soft as a pillow, usually low camber and sometimes low caster.

Drift: It's like racing, but if you purposely make it really hard to drive.
More on that, later.

SWAYBARS:
Another good PI filler is swaybars, but don't underestimate these just yet. I've found many occasions where adding swaybars kept a stock or street suspension in line, keeping the handling tight without sacrificing PI on more suspension.
If you're really maximizing PI, you'll likely run into a circumstance where you can't quite install both swaybars, or can't upgrade both to fit the PI. In these cases, select which to upgrade further based on car characteristics. If oversteer is a problem, you can keep the rear stock and add a racing bar up front. Or, you can keep the front stock and use adjustability on the rear to soften it significantly.

Keep in mind, on rare occasions the rear swaybar takes a bit more PI than the front. (Accurately reflecting the performance gain since the rear bar has a larger effect than the front)



CHASSIS:
Roll cages? I'm not gonna lie, I usually tell myself I can drive out of chassis twist, so more on that, later.

Weight reduction is good. Weight reduction is your friend. But is it overrated in the PI system, like every other game where light builds dominate almost every leaderboard?
Obviously it depends on the vehicle and road layout which is best, but what's best overall, on average?
Is there any "type" that's usually best? (Lightweight build, medium build or heavyweight builds)


TRANSMISSION:
How good your car's factory transmission is will likely play a part in determining which transmission you're getting, but many cars have a transmission option that improves performance, and sometimes allows adjustment, that decreases PI.

Street: Usually just adds an extra gear, other performance is the same. If the engine received camshaft upgrades, the gears may be too long. Stock gears can also be too short, especially if camshafts haven't been upgraded, or large power gains have been made.


Sport: Decreases shift time, adjustable final drive. This means it doesn't matter if the car has long or short gears, as long as an adjustment will fix them you don't need to spend PI on the racing transmission.
Sport often lowers PI or comes with no PI added.
I like the sport option, particularly on cars that take a large PI hit from racing transmissions.


Racing: Fully adjustable, this solves any gearing problem and speeds up shifting more than any other upgrade.
Great for tight tracks, or anywhere lots of shifting is required, and off-road applications. Often, if it doesn't help performance it doesn't hurt the PI.
If the racing transmission doesn't use too much PI, it's always on my car.


Clutch: Aftermarket clutches can save a lot of time in racing, especially for drivers running automatic, or even plain manual without a clutch.
It's a good modification to make, but I wouldn't prioritize this over a better transmission, which usually offers both, quicker shifts and better gears.


Driveshaft: Should reduce drivetrain weight significantly, putting HP gains to the wheels. With a very low PI cost, it's probably not a bad way to go, but works great as a PI filler.
(For example, if you're already at 800PI, you can usually sneak a lighter driveshaft in)


Limited slip differential: At no PI cost to you (none at all) why not?
Especially on 4wd, this can really make your car or truck drive exactly how you want it to.
On older cars, it's almost a necessity to keep the inside wheel from spinning into oblivion.


AERO PARTS:
Aero parts have finally taken a PI hit in FH4, which is exciting. Most cars gain significant performance from added downforce, and the PI system has attempted to address the issue by adding significant PI to many cars, making the decision between speed or handling less one-sided.

Front bumper: Either for looks or for downforce, and sometimes advertised with reduced aero drag.
Adjustable front downforce is key in high speed handling. This can add significant PI, so make sure you'll be driving fast enough to make use of it.

Rear wing: This adds downforce, usually. If a car already understeers it might not be worth it, but for high power RWD cars, it can make a very large difference.
 
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WHEELS & TIRES:
Width upgrade vs compound, which is the PI killer?

Street:
A basic sports tire with progressive sliding, easy to play with but more grip than stock. (At least on some cars)
These tend to add a lot of PI to some cars, most times I would say they aren't worth the 100 PI they can add.
Some cars these only add a few PI, 5-20, in those cases they may be worth it depending on your cars stability needs.

Sport:
A high-level sports tire, still has some progression and play in it, with more grip.
These often cost more PI than rally/snow tires, and offer slightly less performance on road, and significantly less off-road.
So far I will take the rally/snow tires every time.

Racing:
The most grip on tarmac you can get unless you're drag racing. Most unforgiving tire, your slides happen much faster with these.
These can add a LOT of PI, so make sure you actually need the grip, otherwise you can probably make a faster PI car with rally/snow tires.

Rally/Snow:
A great all around performer, on par or better than sports tires on the road, and amazing off road. A solid choice for true versatility.
These are seeming to be the best deal on tires. Sometimes even lowering PI from sports tires, they outperform them in every way except sometimes braking. Since braking has abbreviated distances in Horizon, it doesn't really matter.
The only cars that need more grip on the road are 2wd hypercars, and these leave you with a rally car if you have 4wd.

Drag:
Necessary for high powered 2wd vehicles to be competitive at drag racing.
As for road racing or off-road, I don't actually know yet, more to come.
These can be used for some cars in road racing, particularly something that can't corner well already and needs loads of grip for exit.
They are quite terrible off road, so don't try it.


Width:
Tire width upgrades usually add a usable amount of added grip, without a big PI hit. If a better tire compound adds the same or less PI though, it seems often a compound upgrade is then a better deal.

Track:
Barely affects PI, it's probably worth it? I usually set it to whatever I think is most visually appealing. It should add performance, I'll try some kind of test at some point.



WHEELS:

Lighter is better, and usually smaller is better, at least according to the PI.
I usually use wheel weights and sizes to fit a PI, since I've yet to detect a noticeable difference in performance.
For example, if you're at 801 PI, making the rear wheel an inch bigger can bring you down to 800 PI, or installing heavier wheels can bring you down even farther.



AERO PARTS:

Aero parts have finally taken a PI hit in FH4, which is exciting. Most cars gain significant performance from added downforce, and the PI system has attempted to address the issue by adding significant PI to many cars, making the decision between speed or handling less one-sided.

Front bumper:
Either for looks or for downforce, and sometimes advertised with reduced aero drag.
Reduced drag sounds good, but does it translate to usable speed?



ENGINE/DRIVETRAIN/ASPIRATION SWAPS:

Investigating weight, car balance, total power and power delivery.

Heavy classic muscle cars have a tendency to gain a lot of cornering and stability from lightweight engine swaps for what I assume is a Camaro 6.2l V8. The PI is affected by this, so is it worth it?



AERO PARTS:
Aero parts have finally taken a PI hit in FH4, which is exciting. Most cars gain significant performance from added downforce, and the PI system has attempted to address the issue by adding significant PI to many cars, making the decision between speed or handling less one-sided.

Front wing/bumper: Either for looks or for downforce, and sometimes advertised with reduced aero drag.


Rear wing: These add rear downforce, which is helpful on high powered RWD cars and trucks, and on cars with high speed oversteer.



Forced Induction:
Turbos
: These can add loads of power, but generally add weight to whichever wheels are overloaded already, making the car less balanced.
In cases where the engine can be built to reach your power goal without using forced induction, saving the weight might often be the best solution.

Superchargers: These are similar to turbos, but heavier, less efficient, and usually give less torque.

Both of these options can be used to your advantage with the PI system. Sometimes cutting torque and adding weight is exactly what a car needs to fit a PI, and sometimes you might need a turbo to maximise performance.



Drivetrain swap: RWD or AWD

AWD: This can turn any difficult car or truck into a dream, and offers performance benefits 2wd can only dream of.
More beneficial to higher powered cars, the PI usually reflects the same.
Keep in mind that in the right situations, a 2wd build can leave this in the dust, given the right setup, driver, or course.


RWD: Ever wanted to make your Civic RWD? Well you can, although I'm not convinced it's actually a good thing very often, it's definitely fun and can remove that dreaded FWD understeer, but don't expect lots of grip from the back wheels, because they usually have 40% or less of the vehicles weight resting on them.
But it is fun.
 
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Head to Head:

2017 Dodge Ram 2500 Power Wagon
Factory engine @ 600PI
425hp / 445lb-ft / 5,095lbs
Weight distribution 56/44

Vs.

2017 Dodge Ram 2500 Power Wagon
6.2L V8 engine @ 600PI
415hp / 415lb-ft / 5,076lbs
Weight distribution 55/45

Both trucks received nearly identical upgrades and setups, including racing transmission, brakes, driveshafts, swaybars, lightweight wheels and slightly wider front tires.
"Stock" will refer to the 600PI truck with the factory Hemi engine.
"Swap" will refer to the 600PI 6.2l V8 engine swapped truck.


Drag Race:
Almost an exact tie, the 6.2 swap does the trick and takes the trophy, with ever so slightly better acceleration down the winter drag strip.
The 6.2 V8 shows great potential, and what seems to be a better power curve than the Hemi motor.
An interesting note is it seemed like the truck with the stock engine had a little extra wheelspin, keeping me from using the top end of the first two gears compared to the swapped truck.

Drag Race:
Stock: 28.428 @123mph
Swap: 28.295 @123mph


Dirt track:
Still very difficult to distinguish a "best version", the stock engine with more weight on the front seemed to have a little more grip in important places, particularly sharp turn-in.
The Swapped truck feels more balanced, and provided enough grip, it is easier to drive, but a few places pulled the back end out, making it harder to drive in certain situations.
The two trucks took turns winning out, and it's still hard to say the winner was definitely the best truck. The Rivals ghost feature came in handy here, to watch the slightly different layouts push ahead and fall behind in different corners due to each one's strengths and weaknesses.

Mudkickers 4X4 scramble:
Stock: 58.725
Swap: 58.825

I'll be running 700PI setups to see if it shines a brighter light on which is the better format.
 
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Drivetrain weight reduction test

Test car: 02 Ferrari 575M Maranello
Added a tire upgrade and width upgrade, heaviest wheels available installed.

I ran each modification set 3-5 times, with most of the runs for each spec being identical times.


Original (Full weight drivetrain)
12.145 @ 121mph

Wheel reduction (55 lbs / 25ish kg)
12.045 @ 122mph

Driveshaft 10lbs + Clutch* 5lbs
Total reduction 65lbs
12.012 @ 122mph**

Flywheel 5lbs + front wheel width 7lbs
Total reduction 77lbs***
11.959 @ 122mph**

*The clutch was only considered due to the cars flappy paddle transmission, and to increase the drivetrain weight reduction applied.

**The speed did increase slightly with each reduction, just not enough to change a whole mph at the line.

***The front wheel weight is not drivetrain weight, but with this test car only able to remove 5lbs of flywheel weight, it wasn't going to be easy to discern any difference using only that change.
The next test vehicle will have a heavier flywheel and driveshaft.
 
Caster and Camber:
Because caster and camber can be so complicated, I'm going to try to explain in basic terms what they do in FH4, or more specifically how they affect handling.

Because caster changes camber, the amount you use of either directly affects the other.
Optimally, you want to run as close to 0.0 camber as possible in theory, but you'll want some camber on the rear for cornering. Theoretically a perfect setup increases the camber on the front as you turn the wheel, so you won't need a lot of camber, if any, on the front wheels.

Generally speaking in FH4, lowering caster will reduce steering sensitivity, and increasing it will increase sensitivity, or "twitchyness".

Camber plays a roll with this as well. For example, a car at 6.5 caster might be too twitchy and unpredictable with 3.0/2.0 degrees of camber. Either lowering caster or camber will help solve that. You could drop camber to 1.5/1.0, or you could drop caster to 5.5.

The trick is to try to find what works best for you as a driver, and what works best for the car.
Fot example, my Zenvo is running around 2.0/1.0 camber @ 1.0 caster.
My Audi RS6 is running 1.5/1.0 camber @ 6.5 caster.
My Jeep Trailhawk is running 3.0/1.8 camber @ 3.2 caster.
My Alfa Romeo Guilia FE is running 3.0/1.5 camber @ 7.0 caster.

Some cars like high caster and low camber, other like low caster and high camber. Still other cars like low camber and low caster, and of course, some like high caster plus high camber.

I think for the most part you can tell when you have reached a desirable amount of both, the question remains, how do I know if I want less caster and more camber, or less camber and more caster?

I haven't timed it yet, so I can't say for sure. What I can say for certain is that starting with what feels good isn't a bad place to start. There's a lot to be said for a car driving exactly how you want it to.
I do think the sweet spot for most cars is between 1.5-3.0 on the front, and 0.5-3.0 on the rear. Adjusting caster to make the camber work seems possibly more viable than adjusting camber to caster.

I currently aim for around 1.2-2.5 front camber and 0.5-2.0 rear camber, and adjust the caster to a range that works at.
If you want more grip going straight you can definitely reverse the order and bring camber down to 0.0 and raise caster up to your maximum sensitivity that you prefer. I would always recommend at least 0.5 front and rear camber though, because you're not losing much going straight, and there is play that makes some camber almost always useful, as depicted by the rear wheels, which don't have a steering angle yet see cornering benefits from negative camber. (Due to flex etc)
 
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